# difference between phase difference and path difference?

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#1
I don't get what the difference is.
0
11 months ago
#2
Path difference is the difference in distance travelled by the waves (normally expressed in terms of the wave's wavelength)
Phase difference is to do with whether the waves are at a peak or trough (or any where in between) and is often expressed as an angle, with 180 degrees being out of phase (peak meets trough)

I find this helps (better explanation than mine): https://www.youtube.com/watch?v=j1ULNWZ3Xh4 hope that helps
Last edited by tande33; 11 months ago
0
11 months ago
#3
Path difference refers to a physical length, phase difference is dimensionless. If two waves have a phase difference of but have the same wavelength, their path difference is
Last edited by Sinnoh; 11 months ago
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11 months ago
#4
I have forgotten a lot A level Physics since schools closed lol
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#5
(Original post by Sinnoh)
Path difference refers to a physical length, phase difference is dimensionless. If two waves have a phase difference of but have the same wavelength, their path difference is
Oh ok so is path difference measured in wavelength but phase difference measured in radians?
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11 months ago
#6
(Original post by m.s124)
Oh ok so is path difference measured in wavelength but phase difference measured in radians?
That is not wrong but I don't think you could say that was the difference as it would be like saying the difference between distance and time is that one is measured in metres and one in seconds. They are measurement of completely different things
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#7
(Original post by tande33)
That is not wrong but I don't think you could say that was the difference as it would be like saying the difference between distance and time is that one is measured in metres and one in seconds. They are measurement of completely different things/
wait but don't they both measure the length of one wave compared to another?
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11 months ago
#8
(Original post by m.s124)
wait but don't they both measure the length of one wave compared to another?
Not really, I would describe Phase difference as the difference between to waves in their cycle. Whereas, Path difference is a measure of difference in how far they have travelled in terms in their wavelength. https://www.youtube.com/watch?v=j1ULNWZ3Xh4 honestly watch this video, it has diagrams which I can't explain in text. Hope that helps
1
#9
(Original post by tande33)
Not really, I would describe Phase difference as the difference between to waves in their cycle. Whereas, Path difference is a measure of difference in how far they have travelled in terms in their wavelength. https://www.youtube.com/watch?v=j1ULNWZ3Xh4 honestly watch this video, it has diagrams which I can't explain in text. Hope that helps
thank you!!
0
11 months ago
#10
Path difference is the difference in distance ( in metres). Phase difference is the difference in what point the wave is in its cycle (in radians)

Example:
There’s 2 waves, wave X and wave Y,with the same wavelength of 5m. Wave X is 2m ahead of wave Y.
The path difference is 2m.
The phase difference is 2/5*2pi
Last edited by Gerrard88; 11 months ago
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